Variable resistor



June 28, 1960 w. H. BUDD VARIABLE RESISTOR 2 Sheets-Sheet 1 Filed July25, 1958 JMJM W 'VViZbirb 1.25:

June 28, 1960 w. H. BUDD 2,943,288

VARIABLE RESISTOR Filed July 25, 1958 2 Sheets-Sheet 2 WZbarQBudd 37* 8MUnited States Patent VARIABLE RESISTOR Wilbert H. Budd, Elkhart, Ind.,assignor to CTS Corporation, Elkh'art, Ind., a corporation of IndianaFiled July 25, 1958, Ser. No. 750,898

11 Claims. (Cl. 338184) This invention relates to variable resistors ofthe type used in television and radio receivers.

Television receivers, and especially color television receivers, requiremany variable resistance controls for the adjustment of their verysensitive electrical circuits. The majorityof these controls are veryseldom adjusted and, when they are, should be adjusted by a serviceman.Actually, the sensitive receiver circuits which incorporate thesevariable resistors are initially adjusted and aligned at the factory andrarely thereafter is adjustment needed. They have become known,therefore, as preset controls.

Recent advances in color television circuitry have increased the numberof these preset controls required in each receiver. Competition hasforced the set manufacturers to reduce the prices of their sets andinevitably, therefore, the control manufacturers have been beset withdemands from the set manufacturers for lower prices for their controls,and especially their preset variable resistors. Such demands, however,are coupled with the admonition that price reduction must not be at thesacrifice of electrical performance.

Because preset controls are so seldom adjusted, it follows that they donot have to meet rugged structural requirements. This leeway affords anavenue for cost reduction in manufacture, and to take advantage of thispossibility, the present invention has as its purpose to provide avariable resistor which is characterized by a novel relationship betweenits essential parts, whereby certain of the parts have more than onefunction, the individual parts lend themselves well to mass productionat very low cost, and the assembly of the control likewise is simple andeconomical.

Stated in another way, it is an object of this invention to provide alow cost and easily manufactured variable resistor which may be quicklyand easily assembled into a television receiver, and which, nonetheless,is reliably satisfactory in performance.

With a view toward meeting the ever present demand for lower pricedcontrols, variable resistors of the preset type heretofore have beenmade without covers or housings. While this eliminates a piece-part and,hence, an item of cost, coverless or housingless controls are notentirely satisfactory.

This invention achieves the price advantage of a coverless orhousingless control, but nevertheless has its operatinginstrumentalities as eifectively enclosed as in the more expensive andmore conventional variable resistors. To this end, the invention has asanother of its objectives to provide a variable resistor which is sodesigned and constructed that parts thereof which are absolutelyessential, and which heretofore have never served in the capacity of acover or part thereof, are employed for this purpose. These parts,therefore, have a dual function.

Still another object of this invention is to provide a preset variableresistor which is held in its assembled condition through the coactionof its component parts, and without the use of extra securingpiece-parts.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingun- 2,943,288 Patented June 28,1960

derstood that such changes in the precise embodiment of the inventionmay be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

Figure l is a perspective view of a preset variable re sistor embodyingthis invention;

Figure 2 is a longitudinal sectional view through the variable resistor;

Figure 3 is an exploded group perspective view of the component parts ofthe resistor; and

Figure 4 is a cross sectional view through Figure 2 on the plane of theline 4-4, but with the contactor turned to an intermediate position ofadjustment for the sake of clarity.

Referring now particularly to the accompanying drawings in which likenumerals indicate like parts throughout the several views, it will beseen that the variable resistor of this invention comprises essentiallya pair of front and rear end walls 11 and 12, respectively, which arestamped and formed from sheets. of semi-rigid insulating material. Bothof these walls are round and have a round hole at the center, the holein the front wall being designated by the numeral 13, and the hole inthe rear wall by the numeral 19. Each wall also has an annular grooveconcentrically encircling its central hole, the groove in the front wallbeing designated 14, and in the rear wall by the numeral 21. Thesegrooves provide radially inwardly facing annular shoulders for a purposeto be described.

Extending inwardly from the periphery of each end wall is a pair ofnotches 15. The notches 15 are symmetrically disposed with respect tothe centers of the end walls, and their side edges 16 and 17 are allparallel to one another. The bottom edges 18 of the notches aresubstantially tangent to the inwardly facing annular shoulders providedby the outer edges of the annular grooves 14-21. Hence, the junctions ofthe side edges 16, which are the remote or outermost edges, with thebottom edges 18 of the notches form acute angled locating corners.

Confined between the end walls 11-12 is a substantially cylindricalsplit ring type resistance element 22. Preferably the resistance elementis of the wire-wound type, wherein a length of resistance Wire is woundtorroidally upon an initially flat mandrel strip and then curled intoits substantially cylindrical form. In its curled condition, theresistance element 22 thus has inner and outer arcuate faces 23 and 24,respectively, and curved parallel edges 26 and 27.

Prior to curling the resistance element 22 to shape, terminals 28 areattached thereto. The terminals are stamped from sheet metal and eachhas a rectangular body 29 with an integral rectangular bifurcated tang31 extending from one edge thereof. When the terminals are in place onthe resistance element, the body 29 thereof fiatwise overlies the outersurface 24 of the resistance element at the endmost portions thereof,and the tangs 31 are clinched over the ends of the element and havetheir bifurcations pressed down into the inner face 23. This disposesportions 34 of the terminals above and below theedges 2.6 and 27 of theresistance element; and projecting endwise from one of these portions 34of each terminal is a terminal shank 32. The terminal shanks 32 arenarrower than the adjacent portions 34 which results in locatingshoulders 33 facing the ends of the shanks and spaced a substantialdistance out from the adjacent edge 27 of the resistance element.

In assembling the resistance element 22 with the end wall-s 11 and "12,it is of course first curled into its substantially cylindrical shapethen contracted sufficiently to fit into the annular grooves 14 and 21,inserted into the grooves and allowed to expand into snug engagementwith the annularshoulders provided by the outer sides of the grooves.The natural resiliency of the curled element holds it firmly against theouter sides of the grooves, and because of predetermined dimensionalrelationship between the arcuate length of the resistance element andthe location of the notches 15 in the end walls, the portions 34 of theterminals hook themselves into the locating corners of the notches.

The annular grooves 14 and 21, the locating corners of the notches 15,and the natural resiliency of the curled resistance element 22 thuscombine to define the correct positional relationship between theresistance ele- -1nent and the front and rear walls 11 and 12, so thatupon securement of the end walls against separation, a fdrum-likehousing is formed by the end walls and the substantially cylindricalresistance element.

Inside this housing is the rotor assembly of thecontrol. It consists ofan actuator shaft 36 and a contactor '37. The actuator shaft 36 isjournalled in the holes 13 and 19 in the front and rear end walls, andhas axially opposed shoulders bearing against the outer faces of the endwalls to hold the same in place with the resistance element'clampedtherebetween. These shoulders are provided by a flange 38 on the shaftnear its front end, and by flaring the extreme rear end portion 42 ofthe shaft into a rivet head 44, the shaft portion 42 being tubular tofacilitate this flaring operation.

The rear face of the flange 38 is stepped to provide a journal 39 whichis rotatably received in the hole 13 in the front end wall 11, the axiallength of the journal being slightly greater than the thickness of theend wall; and the rear end portion '42 of the shaft is journalled in thehole 19 in the rear end wall 12.

Between its journal portions 39 and 42, the shaft has a driving portion'41 of non-circular shaft cross section. The junction of thenon-circular driving portion 41 and the rear small diameter journal 42forms a rearwardly directed shoulder 43- which bears against a collectorring 46 and holds it in place flat against the inner face of the rearend wall 12. The collector ring is blanked and formed from sheet metal,and has a flat washer-like body provided with a centered hole throughwhich the shaft portion '42 passes. A terminal 47 and a rotationlimiting lug 48 extend perpendicularly from diametrically opposite edgeportions of the collector ring. The lug 48 projects forwardly into thehousing cavity, and the terminal 47 extends rearwardly through aslit-like opening '49 in the rear wall 12 and thereby precludesrotational displacement of the collector ring relative to the actuatorshaft. Externally of the rear wall the terminal 47 has a pair oflocating shoulders 51 flanking its shank 52. These cating shoulders andthe shoulders 33 on the end terminal of the resistance element, arecoplanar and coact to spacially locate the variable resistor on asupport panel (not shown) with the terminal shanks 32 and 52 projectmgthrough holes in the panel for connection with circuits printed thereon.The contactor 37 is mounted on the non-circular drivmg portion 41 of theshaft, and is, of course, inside the housing. It is blanked and formedfrom spring-like sheet metal and it is substantially U-shaped with flatfront and rear arms 54 and 55, respectively, connected by a b1ghtportion 53. The flat arms have non-circular holes 56 through which thenon-circular driving portion 41 of the shaft projects so that thecontactor is constrained to rotate with the shaft between limits definedby the engagement of a tongue 57 projecting from the rear arm 55 withthe lug 48.

Adjacent to the tongue 57 the rear arm 55 of the contactor hasrearwardly directed punctiform contact points 58 which slidingly engagethe collector ring 46. V

'The contactor is so formed that, when free, its. arms Y r ""v 54 and 55are slightly divergent. Accordingly, in the assembled condition of theparts, the contactor is maintained under tension between the rear faceof the front shaft trunnion 39 and the collector ring 46 to assure goodelectrical connection between the contactor and the collector ring.

The contactor, of course, also has sliding engagement with theresistance element. For this purpose a spring finger 59 extends from anedge of the bight S3 with its edges well spaced from the arms 54 and 55.This finger is substantially semi-circular in configuration andpartially embraces the control axis. Its free extremity is formed with arounded contact shoe 61 which rides upon the. inner face 23 of theresistance element 22 to vary ward projection with a screw driver slitin its front end.

From the foregoing description taken in connection with the accompanyingdrawings, it will be readily apparent to those skilled in this art thatthe variable resistor of this invention achieves the desired low costthrough dual utilization of parts, and simplification of assembly,neither of which entail a reduction of quality and performance sonecessary in controls of this type. It will also be seen that, becauseof its dual utilization of parts, the instrumentalities of the controlare effectively housed without the need for separate housing parts.

What is claimed as my invention is:

l. A variable resistor comprising: a pair of spaced apart end walls; arotatable actuator shaft journalled in axially aligned holes in the endwalls; a contactor carried by the shaft between the end walls and having'a radially outwardly biased contact finger; a substantially cylindricalsplit ring resistance element concentrically encircling the shaft andhaving its opposite edges engaged by the end walls, so that said endwalls and the resistance element form an enclosure for the contactor,the contact finger traversing the inner surface of said resistanceelement as the shaft is turned; axially opposed facing shoulders on theshaft bearing against the end walls to hold the same clamped against theedges of the resistance element; and terminals electrically connectedwith the contactor and at least one end of the resistance element.

2. A variable resistor comprising: a substantially cylindrical memberhaving means thereon providing an arcuate resistance path which isconcentric to said member and on the inner surface thereof, saidcylindrical member having a uniform length so that its opposite ends liein planes normal to the axis of the member; a pair of parallel spacedapart end walls separate from but having the cylindrical member disposedtherebetween; an

walls and releasably clamping them against the opposite ends of saidcylindrical member so that the end walls and the cylindrical membercoact to form a housing; abutment means on the end walls to hold thecylindrical member and the resistance path thereon in concentricrelationship with the shaft; a contactor carried by the shaft withinsaid housing and having a radially outwardly biased contact fingerbearing on said resistance path; and terminals electrically connectedwith the contactor and at least one end of the resistance path.

3. A variable resistor comprising: a housing having side and oppositeend walls fabricated from separate parts, the end walls beingsubstantially parallel and spaced apart a predetermined distance; anactuator shaft rotatably journalled in said end walls; abutments on theshaft engaging the end walls to hold them against separation beyond saidpredetermined distance; a substantially cylindrical member having alength substantially equal to said predetermined spacing of the endwalls and being axially confined between them to hold them against saidshaft abutments and against movement toward one another, saidcylindrical member surrounding the shaft and having means thereonproviding an arcuate resistance path on the inner surface of the member;interengaging means on the end walls and said cylindrical member holdingthe latter concentric with the shaft, so that the end walls and thecylindrical member therebetween coact to form a housing for the variableresistor, the side wall of which housing is provided by said cylindricalmember; a contact finger carried by the shaft and biased outwardlytherefrom into pressure engagement with the resistance path on saidcylindrical member to traverse the same when the shaft is rotated; andterminals on the housing electrically connected with the contact fingerand with at least one end of the resistance path.

4. The variable resistor of claim 2 wherein the contactor comprises aU-shaped stamping having substantially fiat arms connected by a bight,said arms having aligned holes through which the shaft passes, at leastone of said holes and the portion of the shaft received therein being ofcomplementary non-circular shape to provide a driving connection betweenthe shaft and the contactor; and the contact finger being an integralextension of the bight.

5. In a variable resistor: a pair of end walls; a substantiallycylindrical side wall separate and distinct from said end walls andhaving its opposite edges engaged by the end walls; means connected withthe end walls holding them firmly against the opposite edges of the sidewall so that the end walls together with the side wall form a drum-likehousing; means providing a resistance path on the inner face of the sidewall; a control shaft for the resistor rotatable about the axis of thedrum-like housing, said shaft having a part inside the housing and beingaccessible from the exterior of the housing to provide for adjustment ofthe shaft; and a rotatable contactor inside said housing drivinglyconnected with the shaft to be rotated thereby, said contactor having aresilient contact finger bearing upon the resistance path to traversethe same as the contactor is rotated.

6. In a variable resistor, the structure set forth in claim 5 furthercharacterized by the fact that the control shaft is journalled incoaxial holes in the end walls; and by the provision of radiallyinwardly facing annular shoulders on the inner faces of the end wallsconcentric with the coaxial holes and engaging the external edgeportions of the side wall to hold the side wall cylindrical andconcentric with the shaft axis.

7. In a variable resistor, the structure set forth in claim 6 furthercharacterized by the fact that the side wall is an initially fiat stripof material possessing a degree of resiliency tending to maintain thesame flat, said strip being curled into substantially cylindrical formwith its ends unconnected so that the inherent resiliency of the striptending to straighten it out holds the same firmly against the radiallyinwardly facing annular shoulders on the end walls.

8. In a variable resistor the structure set forth in claim 7 furthercharacterized by the provision of terminals for the resistance pathfixed to the end portions of said strip which forms the side wall, inelectrical engagement with the ends of the resistance path, saidterminals having portions thereof projecting beyond at least one edge ofthe side wall forming strip; and the end wall engaging said edge of theside wall having notches in its periphery in which said projectingterminal portions are received to secure the side wall againstrotational displacement.

9. In a variable resistor, the structure set forth in claim 8 furthercharacterized by the fact that the terminals have portions projectingbeyond both edges of the side wall forming strip and by the fact thatboth end walls have circumferentially spaced notches in theirperipheries in which said projecting terminal portions are received, thebottoms of said notches being substantially tangent to the annularshoulders and the remote sides of said notches forming acute angles withthe bottoms of the notches so as to better retain the projectingterminal portions in said notches.

10. In a variable resistor, the structure set forth in claim 5 furthercharacterized by the fact that the control shaft is journalled incoaxial holes in the end walls, and by the fact that the contactor ismounted on the shaft between the end walls and comprises a substantiallyU-shaped stamping having spaced apart overlying arms apertured toreceive the shaft, the resilient contact finger being an integralextension of the bight of said U-shaped stamping; and a terminal for thecontactor on the exterior of the housing electrically connected with thecontactor.

11. In a variable resistor, the structure set forth in claim 10 furthercharacterized by the fact that the spaced arms of the contactor throughwhich the shaft passes are biased away from one another and confinedunder spring tension between the end walls, and further by the fact thatthe means electrically connecting the contactor with its terminalcomprises a collector ring overlying the inner face of one of said endwalls and confined between it and the adjacent arm of the contactor, theterminal for the contactor being integral with said collector ring andprojecting outwardly therefrom through the adjacent end wall.

References Cited in the file of this patent UNITED STATES PATENTS2,257,979 Rubenstein Oct. 7, 1941 2,737,560 Mucher Mar. 6, 19562,790,882 Siegel Apr. 30, 1957 2,814,705 Eshelman Nov. 26, 19572,861,158 Jarvis Nov. 18, 1958 FOREIGN PATENTS 659,778 Great BritainOct. 74, 1951

